The International Journal of Engineering and Science (The IJES)

The International Journal Of Engineering And Science (IJES)
II Volume II 2 lllssuell 12 II Pages II 85-91 II 2013 II
ISSN (e): 2319 - 1813 ISSN (p): 2319 - 1805

A New Approach Based on Sinusoidal PWM Inverter with PI
Controller for Vector control of Induction Motor

Nirban Chakraborty, Prof. Goutam Kr. Panda, Prof. Pradip Kr. Saha

1 PG Scholar, Department of Electrical Engineering, Jalpaiguri Government Engineering College, Japlaiguri

West Bengal, India, Pin-735102

2 HOD and Professor, Department of Electrical Engineering, Jalpaiguri Government Engineering College,

Japlaiguri, West Bengal, India, Pin-735102

3 Professor, Department of Electrical Engineering, Jalpaiguri Government Engineering College, Japlaiguri,

West Bengal, India, Pin-735102

ABSTRACT

This paper is mainly based on the vector control of Induction motor (IM). The analysis of mathematical model
of IM, with the powerful simulation modeling capabilities of Mat lab/ Simulink is given here. The entire
module of this IM is divided into several independent functional module such as IM body module, Inverter
module, coordinate transformation module and Sinusoidal pulse width modulation (SPWM) production
module and so on. With the help of this module we can analyze a variety of different simulation waveforms,
which provide an effective means for the analysis and design of the IM control system.

Keywords - Clarke Transformation, Park Transformation, Mathematical model of Induction motor,
Sinusoidal pulse width modulation, Vector control.

Date of Submission: 28 November 2013 "^ ^> Date of Acceptance: 15 December 2013

I. INTRODUCTION

Among all types of ac machine, the Induction machine (IM), particularly the cage type, is most
commonly used in industry. These machines are very economical, rugged and reliable and available in the
ranges of fractional horse power (FHP) to multi -megawatt capacity. Low-power FHP machines are available in
single-phase, but poly-phase (three-phase) machines are used most often in variable -speed drives. In vector
control the IM can be controlled like a separately excited dc motor, brought a renaissance in the high-
performance control of ac drives. In vector control the Magnetic field can be decoupled to get a good control
performance, hence the torque and flux can be controlled independently [6]. The analysis of mathematical
model of IM, with the powerful simulation modeling capabilities of Mat lab/ Simulink, the IM control system
will be divided into several independent functional modules such as IM motor module, inverter module,
coordinate transformation module and SPWM production module and so on. By combining these modules, the
simulation model of IM control system can be built.

II. STATIONARY TO ROTATING REFERENCE FRAME TRANSFORMATION

Three phase ac machines conventionally use phase variable notation. For a balanced three phase, star
connected machine we have-
f a +f b +f c =0

B axis * :>, axis

axia

Stationary axis

C axis '

Fig. 1 . Current space vector in stationary and rotating reference frame

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A New Approach Based on Sinusoidal PWM Inverter with PI Controller for Vector control of Induction Motor

Where f a , f b and f c denote any one of current, voltage and flux linkage [1].

1-

III. CLARK TRANSFORMATION

The transformation from three-phase to two-phase quantities can be written in matrix form as:

2/3

1 -1/2 -1/2
VI/2 -V3/2

(1)

Where f a and fp are orthogonal space phasor. The stator current space vector is defined as the complex
quantity [1]:

h=^+Jh (2)

It is possible to write (2) more compactly as:

i 3 = 2/3(i L ±ai b +a z i c -) (3)

Where i a , i b and i c are instantaneous phase currents and a is a vector operator that produces a vector
rotation of = (27r)/3. The choice of the constant in the transformation of equation (1) is somewhat arbitrary.
Here, the value of 2/3 is chosen. Its main advantage is that magnitudes are preserved across the transformation.
The inverse relationship is written as:

1

-1/2 VI/ 2
-1/2 -V3/2.

(4)

Transformation equations (1) and (4) are known as the Forward Clarke Transformation and Reverse
Clarke Transformation respectively.

IV. PARK TRANSFORMATION

For the transformation of stationary stator variables to rotating reference frame we use park
transformation and then we write in matrix form as:

,/q.J ~~ L- sin B r cos B r J [fjjl

(5)

Where Gr is the angle between stationary reference frames and rotating reference frame is shown in
Fig.l. Transformation equation (5) is known as Park transformation.

V. MATHEMATICAL MODEL OF INDUCTION MOTOR

The mathematical model of an IM [6] in terms of phase voltages for stator and rotor can be written as:

For stator:

(6)

For rotor:

^'itff^ =r r l cii€ H~P^ zh:r (7)
The flux linkage can be written as in matrix from:

Pates 1 _ pss ^sr 1 [ : c ocs 1
The flux linkage equations are:

(8)

-

(9)

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A New Approach Based on Sinusoidal PWM Inverter with PI Controller for Vector control of Induction Motor

Where,

(10)

-Was l*+l

(11)

cos 6,

cos (a - 1200

cos'jS, + 1200 cosCe, - 120=J

cos(e r 4- 120=] cos(G r - 1200"
cos9 r cos(8 r +- 1200

cos

(12)

L ym — Ly

cosfi 1 ,. eos(e r - 1200 cos(0 r +■ 1200"

cosfe- + 1200 cosfl, cos(6- - 1200

cosfe. - 1200 cosCa + 1200

COS

(13)

-%^. r f [r -:~. -m mr

(14)

Now applying the transformations (1) and (5) to voltages, flux linkages and currents in the equations
(6), (7), (9) and (10) we get a set of simple transformed equations as:

The voltage equation in q-d reference frame:

ffls = r s i qs + P^qs + toAds (15)

v ds =r s i ds + pA^ - wk v ( 1 6)

V = r r V + P*qr + (w-ruO^dr (I 7 )

v dr = r r i ir + pA dr - (a - ai r ~)A t , r (18)
The flux linkage equation in q-d reference frame:

^■-jjs = ills "I" ^jw^j;s "I" ^jtfhjr (l^)

^ = (( b + £ M )id i + i M idr (20)

•^ijr = ^M^ifs +('lr + ^Jif )' jr (21)

A*. = t Jf ii ! +Ci I r + iM]|idr (22)

Here, 1^ and L H are leakage and mutual inductance respectively, m is the synchronous speed and <^ r is the
speed of the rotor

The electromagnetic torque {I ; ) for rotor current can be written as:

r s = (3/2)(P/2)(i^ i: -, r - (23)

The electromagnetic torque (1 5 ) for stator current can be written as:

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A New Approach Based on Sinusoidal PWM Inverter with PI Controller for Vector control of Induction Motor

The equation for motor dynamics is:

(24)

(25)

VI. VECTOR CONTROL

Vector control is also known as decoupling or field orientated control. Vector control decouples three
-phase stator current into two phase d-q axis current, one producing flux and other producing torque [2]. This
allows direct control of flux and torque [5]. In case of vector control of an IM drives operates similarly like a
separately excited dc motor drive. In a dc machine, neglecting the armature reaction effect and field saturation,
the developed torque is given by

A

led
'I i ."

1 =W f

Fig. 2. Dc motor model
(26)

Where l a = armature current and ; r - = field current. The construction of a dc machine is such that the

J

field flux tp f produced by the current f* is perpendicular to the armature flux <3 ; , which is produced by the
armature current l a [3] . These space vectors, which are stationary in space, are orthogonal or decoupled in
nature. So in case of an IM the phase currents are decoupled in q-d reference frame for vector controlling. The
dc motor model is shown in the fig.2. [4]

When three-phase voltages are applied to the machine, they produced three-phase fluxes both in the
stator and the rotor. The three-phase fluxes can be represented in a two-phase stationary (c — 8 ) frame. If
these two phase fluxes along {o. —3) axes are represented by a single-vector then all the machine flux will be
aligned along that vector. This vector is commonly specified as d-axis which makes an angle with the
stationary frame G-axis, as shown in the fig. 3. The q-axis is set perpendicular to the d-axis. The flux along the
q-axis in case will obviously zero. The phasor diagram fig. 3 presents these axes. When the machine input
current change sinusoid ally in time, the angle keeps changing. Thus the problem is to know the angle
accurately, so that the d-axis of d-q frame is locked with the flux vector.

Fig. 3. Phasor diagram of a field orientated system

The controller part of the vector control of IM is inverse transformed from q-d reference frame to or- jff
reference frame and then to the stationary phase voltage frame which is then given through a inverter to the
machine model part.

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A New Approach Based on Sinusoidal PWM Inverter with PI Controller for Vector control of Induction Motor

VII. SINUSOIDAL PWM

Fig. 4. shows circuit model of three phase PWM inverter [5] and Fig.4. Shows waveforms of carrier
signal (V tri ) and control signal (V oontro i), inverter output line to neutral voltages are V AO , V B0 , V C o, inverter
output line to line voltages are V AB , V bc , Vca respectively.

Vdc

Va
Vb
Vc

T4

Fig.4. Three phase PWM inverter

- 1 1 —

j_LiMMnnnnnnnnnjTMi±±u

nnnjmiiiMMn^nnnnnnnnj

miTmnnnnnuji i

munnnr

iniimjiJLiuuiiiJinjinii

iul

MLiriMTirmmmjiLrL

nun

Fig. 5. Waveforms of three phase sinusoidal PWM inverter

The inverter output voltages are determined as follows:
When V control > V tn , V AO = V DC /2
When V control < V tn , V AO = -V DC /2

Where V AB = V AO -V BO , V BC = V BO -V co , V CA = V co -V ao .

VIII. FIGURES AND TABLES

Here we take the base speed as 200rpm and we observe form the waveform of the speed that the rotor
speed almost gives the desired response. The total simulation time of the motor is t=0.4sec. In current wave
form we see that the three phases current almost perfectly merge with each other. We also observe the
electromagnetic torque, inverter output voltage waveform and dq axis current waveform

We take Stator resistance (rs) = 6.03, Rotor resistance (rr) = 6.085, Stator inductance (Ls) = 489.3e-3, Rotor
inductance (Lr) = 489.3e-3, Poles (P) = 4,

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A New Approach Based on Sinusoidal PWM Inverter with PI Controller for Vector control of Induction Motor

Fig 6: Three Phase Current response curve

y

Fig 7: Speed Response curve

Fig 8: Electromagnetic Response Curve

Fig 9: Inverter Output Voltage Waveform

Fig 10: d-axis current Waveform

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A New Approach Based on Sinusoidal PWM Inverter with PI Controller for Vector control of Induction Motor

Fig 1 1 : q-axis current Waveform

IX. CONCLUSION

In this paper vector control has been described in adequate detail and has been implemented on IM in
real time. The performance of the IM is quite satisfactory by using PI controller and Sinusoidal pulse width
modulated inverter. The selection of the value of the proportional gain and integral gain has a significant
impact on the model performance. By varying the inverter voltage we can get steady response for high speeds
also. The performance of vector control is quite satisfactory for achieving fast reversal of IM even at very high
speed range.

REFERENCES

[1] J.Holtz, "Sensorless control of Induction Motor Drives" Procedings of IEEE, Vol.90. No 8, August 2002, PP 1359-1394.

[2] M.Jemli, M.Boussak, M.Godda and M.B.A.Kamoun "MRAS Identification Schemes for Sensorless Indirect Field Oriented Contorl

of Induction Motor Drives With Rotor Resistance Tuning" Proc.of ICEMJurkey 1998 PP 1572-157
[3] S.Tamai, H.Sugimoto, and M.Yano, "Speed sensorless vector control of induction motor with model reference adaptive system," in

Conf.Rec.IEEE-IAS Annu. Meeting, 1987, pp. 189-195.
[4] Bimal K. Bose, "Modern Power Electronics and Ac drives".

[5] R. Krishnan, "Electric Motor Drives".

[6] Amresh Kumar Ray, Kaushal Prasad and Nitish Kumar "The Application of Variable Frequency Drive as an efficient control element

in cement industry" in the LIES ||Volume 2||Issue 8||50-56II2013, ISSN (e): 2319-1813 ISSN(p): 2319-1805.

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